When it comes to boosting the value of an NFL franchise, forget Super Bowl wins – it’s all about the stadium.

The New York Giants and New York Jets both catapulted into the top five ranking of most valuable National Football League franchises largely thanks to the teams’ new stadium.

According to Forbes magazine’s annual valuation of the 32 professional football teams, the Giants were the fourth most valuable NFL team at $1.178 billion, while the Jets came in fifth at $1.170 billion. Last year, the Giants ranked eighth and the Jets ranked 10th.

Both New York teams saw their worth surge a league-busting 21 percent over the last year, fueled mainly by the new stadium, which is scheduled to open in 2010.

Their gains come as the average value of an NFL team has climbed to $1 billion this year from $288 million 10 years ago, according to Forbes.

By comparison, only one baseball team – the New York Yankees – is worth more than $1 billion. The most valuable basketball team, the New York Knicks, is worth $608 million, and hockey’s priciest team, the Toronto Maple Leafs, is pegged at $413 million.

Forbes attributed the astounding growth in the worth of NFL franchises to higher ticket costs and new stadium sponsorship deals.

For the second year in a row, Jerry Jones’ Dallas Cowboys rank as the NFL’s most valuable team, growing 7 percent from 2007 to an estimated $1.6 billion.

Daniel Snyder’s Washington Redskins, which held the top spot for seven straight years before being unseated by the Cowboys in 2007, were second with a $1.5 billion valuation.

The New England Patriots were No. 3 with $1.3 billion.

Just as the construction of a new stadium helped the Cowboys leapfrog the Redskins last year, the biggest gainers this year – the Indianapolis Colts, the Giants and Jets – all benefited from new buildings.